The inventive concept generally relates to semiconductor memory devices. More particularly, the inventive concept relates to semiconductor memory devices including at least one on-die termination circuit, and memory systems including such semiconductor memory device(s).
Many contemporary memory systems include one or more semiconductor memory devices configured to transmit/receive data and control signals with a memory controller via one or more signal buses or varying configurations (hereafter, singularly and collectively denoted, regardless of specific configuration as a “bus”). In this context, a bus is any conductive element (e.g., wire, trace, pad, bump, via, semiconductor region, etc.) or collection of conductive elements intended to communicate one or more electrical signal between circuit points. As is well understood by those skilled in the art, the higher the frequency of the signal(s) being transmitted between circuit points (e.g., between a memory controller and related semiconductor memory devices), the greater the amount of distortion experienced by the signal(s).
Much of the signal distortion experienced at higher frequencies is associated with signal reflections and other noise resulting from mismatched impedances at different ends of a bus. To alleviate impedance mismatches and the resulting noise, signal lines of a bus undergo a “termination” process wherein a resistor and/or other discrete element is provide to better match the impedance of the signal line, thereby preventing or reducing signal distortion. Yet, the provision of termination elements on a bus has certain drawbacks, such as increased current consumption.